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Tacho issue

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AlanL

New member
Hi there, I am new to the forum.
I have read heaps of threads on the topic, but I am stumped with this problem.

Mariner 50, 1996. (3 cyl).
Lost tacho, while engine running, at sea. ie had not been fiddling with anything. It did this before some years ago. replacing rectifier fixed it. It is the Red stator (high output version).
Replaced rectifier, no change.
So have done as much diagnostic as I can with my multi meter.
Engine is chrging. 13.2V at rest, 14.5 at idle.
Approx 1 ohm between yellow stator wires - ie no broken wire.
Tach zeros out when I put 12v to grey wire.
Grey wire on to either yellow stator wire, still no tach.
Maybe tach is broken.
BUT, I am only getting 2vAC at the grey wire out of rectifier. I think I should get more (4+?).
Tach moves when engine cranks. But dies when engine fires.
Any ideas would be useful.
Thanks
Alan
 
haventaclue said:
Morning AlanL,welcome to the forum.
Test for rectifier http://www.themarinedoctor.com/yabbfiles/Attachments/rectifier_test.jpg .The output on the gray wire should pulse.Check and clean the grounds on both rectifier and tach.But I think the tach is fried.
Click to expand...

Many thanks for the reply. What should I be measuring the grey output as - I had it on AC.
In the very useful link of test values you gave me, it quotes 4v+ for trigger voltage, but the header for the column says DVA - how do I measure DVA?

The test procedure for my rectifier is not per the normal schedule I find in the manuals - I have one of those 6 wire epoxy sealed block things - two yellow, two reds, and a black and grey wire - so I am not sure how to test for that one.
Other than it is new (hopefully OK) and battery is charging.

I agree, tach may be fried - have spent ages trying to diagnose issue - may be quicker to try and find another tach to try - not easy.
Thanks
Alan
 
You need a DVA meter or an adapter to measure peak voltage.There is a lot of youtube videos on how to make your own.A known working tach is the easiest way to test,or take yours to a boat with a known working tach.
 
OK, swapped a tach over. Still no go. I am getting 12v between the purple wire on tach, and Gnd on tach, and 14.2 V when motor idling. This would suggest the problem is with the grey/SND wire - the one from the regulator? But the unit is obviously charging and the regulator (new) has done no running other than test the tach. For all I know the old regulator is OK too, I just swapped it out because the tach had stopped.
Anyone got any info on how to test the 6 wire epoxy regulator?
Where else in the circuit should I be looking for the fault?
Maybe I need to find a peak voltage meter.
Thanks
Alan
 
Do a continuity test on the gray sig wire from the tach to the engine.If output is increasing with the engine running,that would rule out a stator problem,unless it goes really high,above the regulated 14.4v.Test the same as the three post one,using the two yellow and the male red + and the black ground instead of the base as described in the link I posted.New rectifiers have been known to be bad as well.You could also run a fresh wire from the gray from the rectifier/regulator to the tach sig,see if that works.
 
Haventaclue - many thanks for the helpful advice. Problem found. Simplest of issues and I go looking for complicated answers. There is a break in the grey wire somewhere. I have been testing at the regulator output junction. I get output at the regulator. But between there and the tach there is a discontinuity. All I have to do now is find it.:confused: Now all the symptoms make sense.
I would like to know how to test the 6 wire regulator though. I have two yellows and two reds. Any idea how I tell which red/yellow is which and how these relate to the old version terminals?
Thanks for the help, this was driving me nuts. Have spent HOURS on it. Hate to think what a boat shop would charge me.
Regards
Alan
 
The two yellow wire = terminals a & c. The red wire with the male bullet connector = terminal a. Black wire is = base/f, as shown in the rectifier test link.
Ignore the grey wire,that is the tach sig. and is connected to a or c inside the rectifier. Ignore the red wire with the female bullet connector,that is for a sensor,haventaclue which:D
 
OK, thanks again. Tach now working. What a pig - broken wire right inside connector pin behind remotes box!
Took a few hours to rectify. But feel MUCH better now problem is diagnosed and sorted.
My picture of the old regulator wiring has two stator terminals (a&c) and a +ve terminal (e). Presumably this is the male bullet connector? and the yellows are on what would be a &c .
" The red wire with the male bullet connector = terminal a." - this leaves me with two terminal (a).
Regards
Alan
 
No, you are correct - one male red, one f/male red.
Just that you have given me two yellow terminals = a & c and a red male terminal = a.
This gives me two 'a' terminals. Did you mean 'e' for the male red?
Further tho, checking my wiring diag it shows both red terminals hooking into the same spot - what they call a 'ground'. Looks like an isolating switch in the pic, but I guess it is an earth.
The only difference in the wiring diag is that my regulator has an extra black (earth) wire - ie 6 instead of 5.
Tried to paste a pic of that part of the diagram - but beyond my computer skills.
Just trying to clarify the wiring of the 6 wire epoxy regulator.
Thanks
Alan
 
:eek:Typo,yes male red = e.
I reread your initial post,you have the tach hooked to one of the yellow stator wires,correct? Have a closer look at those "black" wires,one of them is grey.That is the one you hook your tach sig to.
I dug out the "SELOC".and here's what it says for 3cyl models 50 and 60 HP since 1991.
Two yellow connects to stator,one red to a 20amp fuse,one red to starter solenoid,battery side,grey to tach sig and black to ground/earth.So according to "SELOC",it doesn't matter which red you use. I should have looked there before I opened my big mouth:eek::D
 
Thanks for the terminal clarification. And my tach is working fine now thanks to your advice. So just trying to clarify the rectifier thing for future as I have had issues with it before. The tach is hooked in to the grey wire - this is the culprit of the initial problem - had broken at the back of a pin in a terminal connector.
Can't quite understand the red wiring. Your SELOC description sounds correct for my engine. The 50 HP '96 Mariner manual I pull up has the same red wires going to an Earth. Both of them off to the same earth terminal. Wish I could copy and paste the pic but my lack of computer skills won't let me. However that picture has a rectifier block with only 5 wires (no black earth wire). Weird. But from what you say it seems hard (for me) to deduce which of these dual yellows and reds I should be testing between to compare to the old style terminals a,c,&e. Or should I get the same answer either way? Have tried the process with the rectifier I removed and can't get it to do similar numbers to those book values for old type. In fact I get a weird cycling of ohms with one of the tests - rises and falls while you watch it.
I don't mind if this is in the too hard basket, but if we could get a clear picture of how to test this rectifier, it would be helpful, to me at least, and maybe others.
Regards
Alan
 
I wouldnt trust anything in a Seloc manual, below is the troubleshooting for that rectifier....

Troubleshooting Tachometer
1. At 800-1000 RPM, check output on the gray wire, reading should be at least 8 volts with a DVA meter. A low reading
usually indicates a bad regulator if the system is charging the battery.
2. Check the resistance between the gray wire and engine ground. You should read above 100K (100,000) ohms. Gray
to red, and gray to the yellow wires should be a high reading, usually in the M range
Bench Test
Diode plate check: Test the forward diodes between the two yellow wires and the red wire. You should get a reading of
about 45K (45,000) on one and a high reading on the other. Check the resistance from each of the yellow wires to case
ground, you should get a reading of about 56K (56,000) on one and a high reading on the other. The red wire should read
about 14K (14,000) ohms to ground.
Tachometer Circuit:
Check the resistance between the gray wire and engine ground. You should read above 100K (100,000) ohms. Gray to
red, and gray to the yellow wires should be a high reading, usually in the M range
Thank you for using CDI Electronics 7/20/2010
 
Many thanks faztbullet and havent a clue for your time and info. Sorry I didn't reply earlier faztbullet, but for some weird reason your post never turned up in my inbox.
Thanks again.
regards
Alan
 
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